Over-indulgING during the festive season is good news for gym owners with business booming as former couch potatoes push themselves to the limit to shift the excess poundage.

Going hell-for-leather on a treadmill to lose the festive flab may seem the healthy way to kickstart 2002, but in truth it could have a devastating effect on your health.

The Arthritis Research Campaign has recently voiced concern that binge exercising could actually do more harm than good and amateur gym devotees could risk developing arthritis in later life.

Fergus Logan, chief executive of the Campaign, explains: "We know that people who severely damage cartilage in their 20s and 30s are at greater risk of developing osteoarthritis when they get older. We're not saying 'don't play sport' because overall it's beneficial for health, but it needs to be tailored to people's individual needs. Our advice is don't overdo it now because you might regret it later.

But you don't only risk arthritis if you over-exert yourself. Sharon Stone suffered a stroke last September after a vigorous workout which may have caused a weakened blood vessel to burst, while Douglas Adams, author of The Hitchhiker's Guide To The Galaxy, died at the age of 49 on an exercise bike last May.

Although fatal injuries are extremely rare, injury is not. Mike Walden, sports therapist and founder of website www.sportsinjuryclinic.net says a common problem suffered by binge exercisers is tendon inflammation.

Tendons attach muscle to bone and overuse will cause inflammation. As long as this is looked after then there will be no lasting damage. If, however, you ignore the early warning signs then you may have long term problems, he says.

If you use the wrong technique by lifting weights too quickly or lifting weights that are too heavy you can also suffer painful muscle strains, according to Walden. Not warming up properly is a major cause of muscle strains. A warm-up will increase body temperature muscles work far better at a temperature of 40 degrees C rather than normal body temperature, Walden says.

Back problems often surface in the gym, but Walden believes most of these are related to lifestyle. "One hundred thousand years of evolution has designed the human body to be an active hunter-gatherer and in the space of less than 100 years we spend most of our time sitting on our backsides. This results in adaptive shortening of certain muscles and weakening of others. When we try to exercise our bodies cannot often do what is asked of them, he explains.

Another problem caused by lifestyle changes is endured by women alone. Those who wear high heels for most of the day will have shortened calf muscles. When they run in flat running shoes the Achilles tendon is strained and becomes inflamed, he says.

But despite all of these potential problems it is possible for most people to get in shape. They just need to take things slowly. I believe gyms are fairly safe places as long as you have an instructor who knows what he or she is doing, he says.

Attending a gym induction is vital, according to Corinne Thompson, a health and fitness manager for David Lloyd Leisure. People who join the gym after Christmas tend to come and overdo it. An instructor will give some advice on how many times you should come to start off with, she says.

At David Lloyd Health and Fitness clubs, a health check is carried out before letting new members loose on the equipment. We find out if people have any injuries or health niggles, Thompson explains. This enables instructors to warn exercisers to steer clear of certain pieces of gym equipment which could make their injuries worse.

Individual programmes are then worked out, allowing gym-goers to begin fitness training. Before exercising it is important to eat as not eating enough is a common mistake made by those trying to lose weight. Keep-fitters will actually need to eat more to compensate for their extra exertion, otherwise they may pass out, she warns.

Exercisers should then warm up before they start any vigorous exercise. Thompson suggests between five and seven minutes and urges people to take it slow.

Don't do anything that increases your heart rate too much, she suggests. Then you can get going with your workout.